High voltage current sources are required in almost all AC-DC converters. A high voltage current source generates a charging current by converting a line voltage that is rectified from an AC voltage, such as a 220V AC voltage. A voltage is then generated by charging a capacitor with the charging current, and is further provided to supply a control circuit of a converter during the startup period.
The charging current of the traditional high voltage current source is simply converted from the line voltage, thus, the power dissipation is high and the reliability is bad.
Accordingly, an improved high voltage current source having low power dissipation and good reliability is required.